Field of the Disclosure
The present disclosure relates to a communication apparatus that performs communication via a telephone line, and that includes a line connection terminal to which the telephone line is connected, and a telephone connection terminal to which a telephone is connected.
Description of the Related Art
In various communication apparatuses, such as a facsimile machine and the like, that perform communication via a telephone line, a telephone for a voice call is further connected to the communication apparatuses in some cases. In such cases, the communication apparatuses each includes a line connection terminal to which the telephone line is connected, and a telephone connection terminal to which the telephone is connected. In many cases, however, there are used a line connection terminal and a telephone connection terminal that are the same in shape, the respective terminals are therefore connected to respective wrong connection destinations sometimes, and thus the communication apparatuses do not operate properly. Incidentally, there is known a communication apparatus including a connection unit (hereinafter also referred to as “telephone connection relay”) that controls whether or not a telephone connection terminal is to be connected to a modem unit and a line connection terminal. Japanese Patent Publication No. 5146430 discloses the following method. A line voltage acquired under conditions where a telephone connection terminal is connected by a relay is compared with a line voltage acquired under conditions where the telephone connection terminal is not connected by the relay, and, if the line voltage acquired under conditions where the telephone connection terminal is connected is higher, it is determined that a wrong connection has been made.
Incidentally, a telephone to be connected to the telephone connection terminal typically includes an element (hereinafter referred to as “capacitance element”) having a capacitance component, such as a capacitor or varistor, for various purposes. For this reason, when a telephone line is connected to the communication apparatus, the capacitance element is charged by a line voltage supplied from the telephone line to a value (for example, 48 V) close to the line voltage. In a normal standby state, the telephone is not disconnected by the telephone connection relay, and is connected to the line within the communication apparatus, and thus the capacitance element included in the telephone is charged even if the telephone is subjected to a wrong connection. Even if the telephone line is disconnected by the telephone connection relay under such conditions, electric charges accumulated in the capacitance element included in the telephone subjected to a wrong connection are not discharged quickly. For this reason, in the method described in Japanese Patent Publication No. 5146430, the voltage may not decrease depending on a charge voltage or discharge state of a capacitance element, and, although a telephone is actually wrongly connected to a line connection terminal, it may be erroneously detected that the telephone is correctly connected. In particular, in the case where an exchange is a private branch exchange, a voltage value applied is typically low, a phenomenon in which the value of a reduction in voltage decreases is therefore more conspicuous, and thus the line voltage acquired under conditions where the telephone connection terminal is connected and the line voltage acquired under conditions where the telephone connection terminal is not connected are substantially the same value.